HLB (Huanglongbing or Citrus Greening Disease) is the most devastating disease to affect citrus trees. It infects all varieties and types of citrus, from navel and Valencia oranges, to grapefruits, limes, lemons, clementines, tangerines, mandarins, blood oranges, etc. No citrus is naturally immune. Some varieties are a bit more tolerant that others (meaning that it takes them longer to get sick and die, but eventually die they do).
HLB is an extremely devastating disease in many citrus producing areas of the world, such as Florida in the USA. In other areas like Texas and California, it has been found and either hasn’t been there long enough to cause extensive damage yet, or there is something about the environment on those areas that makes it less severe or progress more slowly.
In all cases, HLB causes fruit drop, reduced crop yield, and eventual tree decline and death.
HLB is believed to be caused by Candidatus Liberibacter asiaticus (CLas), a fastidious bacterium that has not been cultured yet, despite extensive effort by a number of research groups. The “Candidatus” is added to the beginning of the name because it hasn’t been isolated in pure culture yet, so it is possible that what we call “Liberibacter asiaticus (Las)” could be a mixture of different species. We say “believed” because we have not been able to apply Koch’s postulates yet: until we can take isolated, pure cultures of Las and infect citrus trees and cause the same disease symptoms as described for HLB, then we really don’t know for certain that CLas is indeed the cause of HLB. However, the preponderance of evidence to date strongly suggests that to be the case and the scientific community and the citrus industry both proceed accordingly in our efforts to fight this disease.
A number of great descriptions of HLB and CLas are available online, here are a few of our favorites.
If you like orange or grapefruit juice, if you enjoy eating fresh oranges, grapefruit, clementines, or mandarins (“Cuties”, “Halos”), if you like hummus (which has lemon juice in it), if you like naturally flavored citrus sodas, then you should care.
All of these foods are in danger, either of being eliminated from production in North America or of seeing significantly declining production levels. All of that equals either lack of availability in your local grocery store, or huge increases in price.
In addition, citrus production and processing is a very large industry in several states, which employs thousands of workers and impacts a host of downstream industries (shippers and grocers to name the most directly connected). Florida has already seen a several Billion dollar impact on its economy per year as a result of this disease.